CaF2-Al2O3-MgO电渣微结构的原位拉曼光谱及27Al魔角旋转核磁共振研究

In-situ Studies of Microstructure of CaF2-Al2O3-MgO Electroslag by Raman Spectroscopy and 27Al MAS NMR

运用原位拉曼光谱和27Al魔角旋转核磁共振研究了CaF2-Al2O3-MgO电渣重熔渣晶体、玻璃和熔体的微结构及铝配位数的变化.利用X射线粉末衍射分析获得该晶体样品中存在的物相,分别基于密度泛函理论及量子化学从头算分析了S-6530晶体和熔体中相关物相的拉曼振动波数及散射活性,并对其主要振动模式进行了归属.结果表明,S-6530晶体中铝主要以六配位形式存在,并有少量的四、五配位.在升温过程中,其中MgAl2O4物相的Al-O多面体由[AlO6]转变成[AlO4]与[AlO5]共存.Al在熔体和玻璃结构中主要以[AlO4]四面体的形式存在,其占比高达71.1%,相较于其晶态,[AlO5]的占比也增加至28.6%.基于构建的熔体团簇模型的量子化学从头算表明,[AlO4]构型倾向于以Q3,Q4连接方式为主的层状和架状结构,而[AlO5]构型则倾向于单体形式.

The microstructure and Al coordination of crystalline, glassy and molten states of CaF2-Al2O3-MgO electroslag remelting slag were investigated by in-situ Raman spectroscopy and 27Al magic angle spinning nuclear magnetic resonance(MAS NMR). X-Ray diffraction was used to analyze phase of the crystal sample. Raman vibrational wavenumber and scattering activity of S-6530 crystal and melt were calculated based on density functional theory(DFT) and ab initio quantum chemical studies, respectively, and the major vibrational modes were assigned. The results showed that six-fold coordinated aluminum mainly exists in the S-6530 crystal, supplemented by a small amount of four or five-fold coordinated aluminum. During the heating process, the Al-O polyhedron of MgAl2O4 phase is transformed from [AlO6] to [AlO4] or [AlO5]. Al is present predominantly in [AlO4] tetrahedron in both S-6530 glass and melt, the proportion of [AlO4] is as high as 71.1%, compared with its crystalline state, the proportion of [AlO5] also increases to 28.6%. Based on quantum chemistry ab-initio calculation of the constructed molten cluster models, the [AlO4] configuration tends to be layered and frame structure dominated by Q3 and Q4 connections, and [AlO5] configuration remains isolated.